The present invention relates to particle trapping, particularly to trapping of DNA and cells/spores using dielectrophoretic forces, and more particularly to hydrodynamic enhanced dielectrophoretic particle trapping by introducing a side stream of fluid into the main stream of fluid containing particles for forcing the particles closer to electrodes producing the dielectrophoretic forces.
Trapping of DNA and cells/spores using dielectrophoretic (DEP) forces is being considered for performing sample preparation protocols for polymerized chain reaction (PCR) based assays for counter biological warfare applications, as well as for a clinical tool to determine genetic information and other medical applications. A key element of the sample preparation process is to enable controlled concentration and/or movement of DNA, for example, prior to detection. DEP forces are strongest near the electrodes which create manipulating fields. The region of effective force is less than 100 xcexcm from the electrodes. Small channels manufactured to bring the fluid containing the particles close to the electrodes have been considered, but this enhances the probability of clogging the small channels, since biological materials are very sticky and plug channels easily.
The present invention solves the problem by introducing a side stream into the main stream to force or squeeze the fluid containing particles close to the electrodes such that the particles would be affected by the DEP forces, but would allow for a relatively open or larger channel to prevent clogging. The invention utilizes a series of electrodes located along a length of an electrophoretic channel. Since DEP forces induce a dipole in the sample particles, these particles can be trapped in non-uniform fields located along the channel, and which are produced by the electrodes. Thus, the present invention provides for hydrodynamic enhanced dielectrophoretic particle trapping.
It is an object of the present invention to provide enhanced particle trapping using dielectrophoretic forces.
A further object of the invention is to provide hydrodynamic enhanced dielectrophoretic particle trapping.
Another object of the invention is to provide enhanced dielectrophoretic particle trapping by forcing the particle containing fluid close to electrodes which produce the dielectrophoretic forces.
Another object of the invention is to provide hydrodynamic enhanced dielectrophoretic particle trappings by introducing a side stream into the main particle containing stream to squeeze the main stream close to electrodes which produce dielectrophoretic forces such that the particles are affected by the dielectrophoretic forces thereby enhancing particle trapping.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. Basically, the present invention provides for trapping of particles using dielectrophoretic (DEP) forces. More specifically the invention involves a method and apparatus for hydrodynamic enhanced DEP particle trapping. This is accomplished by the use of side stream flows to direct main stream flows. Since DEP forces are effective only very close to the electrodes (less than 100 xcexcm), it is important to direct the cells and DNA close to the electrodes. This is accomplished by the invention by using side stream flows. Use of side stream flows in lieu of making smaller channels reduces the chance of blockage of the flow channels, which is very common in biosystems. The apparatus of the invention includes a series of electrodes, which may be photolithographically patterned along the side of a sample flow or fluidic channel, with an AC field placed between pairs of electrodes. The AC field induces a dipole in the DNA or cell or spore which at certain frequencies, traps the particles along the edges of the electrodes. The sample or incoming flow stream containing the cells and DNA is forced close to the electrodes using a side stream flow, which improves the efficiency of DEP trapping.